Method of refining petroleum oil



' No Drawing.

Patented June 25, 1929.

UNITED STATES PATENT OFFICE. I

ROY CROSS, OF KANSAS CITY, MISSOURI, ASSIGNOR TO GROSS DEVELOPMENT CORPO- RATION, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE.

METHOD OF REFINING PETROLEUM OIL.

This invention relates to improvements in a process and method for refining petroleum hydrocarbons, and refers more particularly to the refining of oils in order to produce a pure, water-White distillate from which have been removed such objectionable properties'as sulphur, gum, coloring matter and the like. More specifically, the method relates to the treatment of crude, unrefined, relatively heavy hydrocarbons used for the production of gasoline or other light hydrocarbon materials by pressure distillation or cracking.

The novelty in the present invention lies primarily in the treatment of hydrocarbons utilized as the charging stock to cracking systems prior to the introduction of such oils to the cracking process; the treatment consisting of subjecting the oil to an acid treat and with or without water washing the same before cracking and subsequently subjecting the distillate obtained to a filtering action with an adsorbent material such as fullers earth, aluminum silicate either treated or otherwise, which have the properties of removing certain objectionable matter from the oil.

In the production of gasoline by cracking certain types of petroleum, the resulting product contains a large amount of sulphur and coloring matter. For example, in the cracking of gas oil made from California petroleum, the raw gasoline commonly contains as much as 0.75% sulphur. In the treatment of this gasoline with sodium plumbite, or a solution of litharge in caustic soda, about 0.10% sulphur is removed, or by treatment with copper treated clay by any of the ordinary methods such as that.

explained in a Patent No. 1,515,733 issued to me on November 18, 1924, the sulphur 'can further be reduced.

One of the most successful methods for removing sulphur is that of treatment with strong or concentrated-sulphuric acid. This, however, has the disadvantage that it causes polymerization and -the gasoline produced has higher gum forming properties than before treatment. In the present cracking process, usin the high sulphur oils of California and exico, an end point gasoline is Application filed December 17, 1924. Serial No. 756,560.

produced without treatment or rerunning, but merely by the control and regulation of the temperatures and pressures and proper fractionation with a regulated control of the overhead temperature. This gasoline complies with all of the standard requirements for motor gasoline such as color, distillation range, gum formation, copper corrosion and doctor test.- However, it has been difiicult heretofore to treat this gasoline so that it contains less than 0.10% of sulphur without the use of large quantities of sulphuric acid followed by washing and distillation. The

sulphur in gasoline and petroleum exists substantially in the various forms as follows:

1. Free sulphur is found in certain Rus sian and Roumanian oils as well as in oils such as those from Luling, Texas, and cerplumbite with which it forms lead sulphide.

It can also be removed by washing with caustic soda or alkalies. A considerable amount of hydrogen sulphide is produced from other compounds in petroleum when undergoing cracking. The removal'of hydrogen sulphide in oil is therefore very simle. p 3. Merca tans. These are known as alkyl hydrosulph1des or thioalcohols having the general formula of RSI-I. With sodium plumbite they form lead mercaptides and" lead sulphide, the .latter in the presence of a small amount of free sulphur. They also are precipitated as mercaptides with other metals such as copper, mercury and silver. -Oxidizing agents convert them into soluble disulphides. They are soluble in concentrated sulphuric acid.

L'Alkyl sulphides (R 8) are soluble in concentrated sulphuric acid and are not affected ordinary metals or oxidizing agents when cold.

5..Alkyl--disulphide (RS dissolve in sulphuric acid and are not afiected by ordinary metallic salts or oxidizing agents when cold.

6. Thiophene (C H S) and related compounds are soluble in concentrated sulphuric acid and are not affected by metallic salts or oxidizing agents when cold and are decomposed with difficulty with copper compounds when hot.

7. Thiophanes (tetra-hydrothiophenes) (C H S) are affected by oxidizing agents such as hydrochlorite and alkyl permanganates to form sulphones (C I-1 .30 They are oxidized and dissolved by concentrated sulphuric acid.

8. Sulphones are readily soluble in sulphuric acid but are not effectively treated with metallic salts.

9. Carbon bisulphide may be treated with oxidizing agents such as sodium hypochlorite most effectively to form sodium sulphate.

10. Sulfoxides sulphuric acid.

11. Sulphonie acids are removed by concentrated sulphuric acid in the absence of water and are removed with difficulty by means of metallic salts. Sulphur dioxide is commonly formed from them in such treatment or by heating. a

12. Sulphur dioxide is soluble in sulphuric acid and is removed by sodium plumbite and by oxidizing agents such as hypochloriteand permanganate.

It will be noted from the above that sulphuric acid is a very effective material for the removal of the sulphur bearing compounds but, as has already been pointed out, it has a rather serious drawback in that it produces polymerized gummy substances in the oil. In most instances, as has been pointed out in my Patent No. 1,515,733 issued November 18th,'1924, copper treated clay will sufliciently completely removesulphur under conditions of high pressure and temperature without the formation of gum and without increasing the end point or in any way disturbing the boiling point range of the material. The cost of this treatment, however, when the percentage of sulphur is (RSO) dissolve readily in very high, is often excessive, as two pounds or more of copper is required for each pound of sulphur to be removed. In the case of one percent sulphur in an oil of approximately three pounds per barrel, at least six pounds of copper will be required. Treatment of oil of this character would therefore be rel-' atively expensive, eventhough the copsper ulbe recovered and reused over and over. phuric acid, on theother hand, is an ideal substance for treatment as it ,is 'cheap andv exists as a liquid. Also, it can be contacted with the .011 very inexpensively and the acid may be recovered at a very small extion is preferably warm. The gas oil is now washed with alkaline chlorinated water and after the water has settled, very rapidly treated with from ten to thirty pounds of 66 B. sulphuric acid. This acid may be allowed to settle thoroughly, or may be treated with about a pound of clay to the barrel and filtered to remove the last traces .of sludge. It is desirable that water is not added until the sludge has been fairly completely remove-d; otherwise, the sulphuric acid compounds become redissolved in the oil. The oil is then preferably treated with lime in a quantity suflicient to counteract the effect of any residual acid remaining in the oil. The oil is then adaptable for use as a charging stock in a cracking system. Subsequent to cracking, gasoline of approximately water-white color and containing not more than 0.10% of sulphur under normal conditions, may ordinarily be obtained. This gasoline is then treated with sodium plumbite and cla or may be treated very lightly and quie ly with an exposure of not greater than thirty seconds to acid, followed immediately by a clay treatment and filtered in accordance with my copending application Serial No. 734,735 filed August 28th, 1924, and the application of Walter M. Cross, Serial N 0. 751,849 filed November the 24th, 1924, in order to remove any of the treating substance remainingin the oil.

The whole treatment of the gas oil outlined may be accomplished in the ordinary continuous agitator according to well established methods for this purpose, the acid being contacted with the oil on the counterflow principle, the oldest being in contact with the rawest oil and the new acid being inlcontact with the morethoroughly-treated o1 i A typical result of this method of treatment is shown by the following sulphur contents at different stages:

. Per cent sulphur. 1. Raw oil 2. 2. Oil treated with doctor solution 2. 50

3. Oil treated with sulphuric acid 0. 35 4. Synthetic crude oil 0.30 2. Raw cracked gasoline 0. 12

. Gasoline treated with sodium plumbite and filtered 0. 05

llhe same raw oil, cracked without prel1 inary treatment, gave the following resu ts:

Percent sulphur.

1. Raw oil 2.75 5. Raw gasoline 0. 70 6. Gasoline after treatment with sodium plumbite 0. 60

the objection of throwing off the boiling range and end point of the product. Any polymerization which takes place by acid in an original charging stock is not objectionable, as the range of boiling points in the distillation is reestablished during the cracking operation. Another advantage of the process, and also a peculiarity, is the fact where the oil is given a preliminary treatment with acid as described, the yield is increased when the oil is cracked. For

example, a treated gas oil low in sulphur,.

yielded, after cracking, 34% of 437 F. end point gasoline; while the same gas oil, which had not been preliminarily treated, after being subjected to identical cracking condisulphur, in contrast with the low sulphur content of the gasoline produced from the treating charging stock.

I claim as my invention:

1. A process of producing refined gasoline, which consists in preliminarily treating a hydrocarbon charging stock suitable for cracking in successive steps with a sodium plumbite solution and with sulphuric acid, and subjecting the oil to a'cracking action for separating out the gasoline content.

2. A process of producing refined gasoline, which consists in preliminarily treating a hydrocarbon charging stock suitable for cracking in successive steps with a sodium plumbite solution and with sulphuric acid, removing the treating materials from the oil neutralizing the acid treated oil and subjecting the oil to a cracking action for separating out the gasoline content.

3. A process of producing refined gasoline, which consists in preliminarily treating hydrocarbon charging stock suitable for cracking in successive steps with a sodium plumbite solution and sulphuric acid, with an intermediate washing step of alkaline chlorinated water, neutralizing the acid treated oil and subjecting the oil to a cracking action for separating out the gasoline content. I

. ROY CROSS. 

